Process for producing amino G acid and amino J acid from tobias acid

ABSTRACT

A novel process for producing 2-amino-6,8-naphthalenedisulfonic acid (Amino G Acid) and 2-amino-5,7-naphthalenedisulfonic acid (Amino J Acid) which comprises heating 2-amino-1-naphthalenesulfonic acid (Tobias Acid) in 100% sulfuric acid, sulfonating the heated mixture with sulfur trioxide at a temperature in the range of 90°C. to 150°C. and hydrolyzing the sulfonation product.

The present invention is directed to a new method for the production of2-amino-6,8-naphthalenedisulfonic acid (Amino G Acid) and2-amino-5,7-naphthalenesulfonic acid (Amino J Acid) from2-amino-1-naphthalenesulfonic acid (Tobias Acid). The twoaminonaphthalenedisulfonic acids are used as intermediates in theproduction of dyes.

When 2-naphthylamine (BNA) is sulfonated in oleum, the sulfonationproducts are principally 2-amino-1,5,7-naphthalene trisulfonic acid and2-amino-6,8-naphthalenedisulfonic acid (Amino G Acid). Hydrolysis of thetrisulfonic acid provides Amino J Acid(2-amino-5,7-naphthalenedisulfonic acid). Thus, using this so-called BNAroute, it is possible to prepare a fixed ratio of both Amino J Acid andAmino G Acid. However, because of the known carcinogenicity of2-naphthylamine, this route is not used. Amino J Acid is primarily madeby the sulfonation of 2-amino-1-naphthalenesulfonic acid (Tobias Acid)with 30% oleum followed by hydrolysis of the intermediate1,5,7-trisulfonic acid. Amino G Acid, on the other hand, is made by thesulfonation of beta naphthol with sulfuric acid and then with 20% oleum,in controlled steps from 15°-80°C., followed by amination by theBucherer Reaction.

We have now discovered that addition of sulfur trioxide to Tobias Acidin hot 100% sulfuric acid provides both2-amino-1,5,7-naphthalenetrisulfonic acid and Amino G Acid. Separationof Amino G Acid and hydrolysis of the trisulfonic acid provides Amino JAcid.

This represents a new method for the preparation of Amino G Acid alongwith Amino J Acid, both from Tobias Acid.

It was previously known that Tobias Acid rearranges in hot 100% sulfuricacid to the 6- and/or 8-sulfonic acid, but it was not known that therearranged product could be further sulfonated by the addition of sulfurtrioxide in hot 100% sulfuric acid to give the 6,8-disulfonic acid.

Depending on the conditions used in the reaction, the ratio of Amino JAcid to Amino G Acid can be varied to favor formation of one or theother. Conditions favoring rearrangement favor production of Amino GAcid, i.e., long periods of heating at elevated temperature prior toaddition of the sulfur trioxide.

Generally speaking, the reaction mixture containing2-amino-1-naphthalenesulfonic acid in 100% sulfuric acid is heated for aperiod of time from about 1 to several hours before addition of sulfurtrioxide at a temperature of about 80°-150°C., preferably 100°-120°C. inorder to rearrange the Tobias Acid to the 6- and/or 8-sulfonic acid. Thesulfur trioxide either gaseous or liquid, preferably liquid, is addedand the reaction continued at a temperature of about 90°-150°C.,preferably 100°-120°C., for a period of at least about 2 hours andpreferably about 5 to 10 hours. The reaction mixture is then dilutedwith water and heated to hydrolyze 2-amino-1,5,7-naphthalenetrisulfonicacid to 2-amino-5,7-naphthalenedisulfonic acid. The products areisolated by conventional methods, as described in the accompanyingexamples.

The rearrangement of 2-amino-1-naphthalene-sulfonic acid to form2-amino-6-naphthalenesulfonic acid, 2-amino-8-naphthalenesulfonic acidor mixtures thereof is conducted under conditions of temperature andreaction time which will vary depending on the desired ratio of the2-amino-6,8-naphthalenedisulfonic acid (Amino G Acid) and2-amino-5,7-naphthalenedisulfonic acid (Amino J Acid) in the finalproduct. For instance, when the rearrangement is conducted at atemperature above 80°C., preferably in the range of 100°C. to 120°C.,for a period of over an hour, preferably 1.5 to 10 hours and mostpreferably 2 to 8 hours, the formation of Amino G Acid in the finalproduct is favored, and consequently a higher ratio of Amino G Acid toAmino J Acid results. However, if the rearrangement is conducted below80°C., the ratio of Amino G Acid of Amino J Acid in the final product isconsiderably lower. The reaction is conducted using a weight ratio of2-amino-1-naphthalenesulfonic acid (or its alkali metal salts) tosulfuric acid in the range of about 1:1 to 1:10, preferably 1:2 to 1:6.

The sulfonation reaction between the rearranged product mixture andsulfur trioxide is carried out at a temperature in the range of 90°C. to150°C., preferably 100°C. to 120°C., for a period of at least an hourand up to 5 to 6 hours. A suitable mole ratio of2-amino-1-naphthalenesulfonic acid to sulfur trioxide for the reactionis in the range of about 1:1 to 1:20, preferably 1:2 to 1:1.

The hydrolysis of the sulfonation reaction product can be conducted byrefluxing the sulfonation reaction product after dilution with water.Alternatively, the diluted sulfonation reaction product can be heated toa temperature in the range of 90°C. to 130°C., preferably 110°C. to120°C. The amount of water used to dilute the sulfonation reactionproduct is not critical as long as the hydrolysis takes place onheating. However, for optimum results, it is preferred that a weightratio of sulfonation reaction product to water, or dilute solutions ofelectrolytes, such as sodium chloride, of at least 1:1, and preferablyfrom 1:1.2 to 1:10 be used.

The invention is illustrated by the following examples.

EXAMPLE 1

A reaction vessel was charged with 51.4 grams (28 ml.) of concentratedsulfuric acid and 30.4 grams (16 ml.) of 30 percent oleum to form 81.8grams of 100 percent sulfuric acid. To this was added 44.6 grams (0.2moles) of 2-amino-1-naphthalenesulfonic acid. The mixture was heated to110°-115°C. and 32.5 grams (19 ml., 0.44 mole) of liquid sulfur trioxideadded dropwise over a period of 45 minutes. The reaction mixture wasthen heated at 110°-115°C. for 6 hours, cooled to room temperature anddiluted with 10 ml. water. The diluted mixture was then heated at 110°C.for 3 hours, diluted with 135 ml. of water and cooled to 15°C. A yellowsolid was formed which was separated by filtration. The separated solidwas dissolved in 200 ml. of water. Thereafter, 40 grams of sodiumchloride was added and the precipitate produced (47.8 grams) wasseparated and dried.

The dried precipitate was found to contain 24.36 grams (0.08 mole) of2-amino-6,8-naphthalenedisulfonic acid and 11.39 grams (0.38 mole) of2-amino-5,7-naphthalenedisulfonic acid. The mother liquors afforded anadditional 6.97 grams (0.023 mole) of 2-amino-6,8-naphthalenedisulfonicacid and 7.73 grams (0.025 mole) of 2-amino-5,7-naphthalenedisulfonicacid.

The overall yield of 2-amino-6,8-naphthalenedisulfonic acid was 51.5percent. The overall yield of 2-amino-5,7-naphthalenedisulfonic acid was31.5 percent.

EXAMPLE 2

This example illustrates that by lowering the reaction temperature ofthe rearrangement of 2-amino-1-naphthalenesulfonic acid, the yield of2-amino-6,8-naphthalenedisulfonic acid in the final product decreasessubstantially while the yield of 2-amino-5,7-naphthalenedisulfonic acidis increased.

A reaction vessel was charged with 62.8 grams (34 ml.) of concentratedsulfuric acid and 37.2 grams (19.3 ml.) of 30 percent oleum to form 100grams of 100 percent sulfuric acid. To this 44.6 grams (0.2 mole) of2-amino-1-naphthalenesulfonic acid was added to form a mixture. Afterheating the mixture to 60°C., 32.0 grams (0.4 mole) of liquid sulfurtrioxide was added dropwise over a period of 35 minutes with thetemperature being gradually raised to 100°C. The reaction mixture washeld at 100°C. for 6 hours and cooled to room temperature. The cooledreaction mixture was diluted with 170 ml. of water and further cooled to20°C. Thereafter, the mixture was refluxed for 3 hours and theprecipitate which formed was separated by filtration.

The overall yield of 2-amino-6,8-naphthalenedisulfonic acid was 9.5percent. The overall yield of 2-amino-5,7-naphthalenedisulfonic acid was46 percent.

I claim:
 1. A process for the preparation of2-amino-6,8-naphthalenedisulfonic acid and2-amino-5,7-naphthalenedisulfonic acid comprising the steps of: (1)heating a solution of 2-amino-1-naphthalenesulfonic acid in 100%sulfuric acid at a temperature of from about 80°C. to about 150°C. toeffect rearrangement of the 2-amino-1-naphthalene sulfonic acid to thecorresponding 6- or 8-naphthalenesulfonic acid, (2) sulfonating thereaction product from step 1 with sulfur trioxide at a temperature offrom about 90°C. to about 150°C. to produce a reaction productcomprising 2-amino-6,8-naphthalenedisulfonic acid and2-amino-1,5,7-naphthalenetrisulfonic acid and (3) hydrolyzing thereaction product of step 2 to convert the2-amino-1,5,7-naphthalenetrisulfonic acid to2-amino-5,7-naphthalenedisulfonic acid.
 2. The process according toclaim 1 wherein the hydrolysis is conducted in the presence of water ata temperature of from 90°C. to 130°C.
 3. The process according to claim1 wherein the weight ratio of 2-amino-1-naphthalenesulfonic acid tosulfuric acid is from 1:1 to 1:10 and the mole ratio of2-amino-1-naphthalenesulfonic acid to sulfur trioxide is from 1:1 to1:20.
 4. The process according to claim 1 wherein the weight ratio ofthe 2-amino-1-naphthalenesulfonic acid to the sulfuric acid is in therange of 1:2 to 1:6 and the mole ratio of the2-amino-1-naphthalenesulfonic acid to the sulfur trioxide is in therange of 1:2 to 1:1.
 5. The process according to claim 1 wherein therearrangement reaction is conducted at a temperature in the range of100°C. to 120°C. and the sulfonation reaction is conducted at atemperature in the range of 100°C. to 120°C.